Self limiting catalyst composition and propylene polymerization process

ABSTRACT

A catalyst composition for the polymerization of propylene comprising one or more Ziegler-Natta procatalyst compositions comprising one or more transition metal compounds and one or more esters of aromatic dicarboxylic acid internal electron donors; one or more aluminum containing cocatalysts; a selectivity control agent (SCA) comprising at least one silicon containing compound containing at least one C 1-10  alkoxy group bonded to a silicon atom, and one or more activity limiting agent (ALA) compounds comprising one or more aliphatic or cycloaliphatic carboxylic acids; alkyl-, cycloalkyl- or alkyl(poly)(oxyalkyl)-(poly)ester derivatives thereof; or inertly substituted derivatives of the foregoing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/568,930 filed on Feb. 21, 2006, which claims priority toPCT/US04/30496 filed on Sep. 17, 2004, which claims the benefit of U.S.Provisional Application Nos. 60/579,529; 60/505,313 and 60/505,314,filed Jun. 14, 2004; Sep. 23, 2003 and Sep. 23, 2003, respectively.

BACKGROUND OF THE INVENTION

The present invention relates to stereoselective Ziegler-Natta catalystcompositions for use in the polymerization of propylene having improvedcontrol over polymerization activity and reactor process continuitythrough the use of carefully chosen mixtures of selectivity controlagents (SCA) and activity limiting agents (ALA).

Ziegler-Natta propylene polymerization catalyst compositions are wellknown in the art. Typically, these compositions include transition metalmoieties, especially titanium, magnesium and halide moieties incombination with an internal electron donor (referred to as aprocatalyst); a co-catalyst, usually an organoaluminum compound; and aSCA. Examples of such Ziegler-Natta catalyst compositions are shown in:U.S. Pat. Nos. 4,107,413 4,115,319; 4,294,721; 4,330,649 4,439,540;4,442,276; 4,460,701; 4,472,521; 4,540,679; 4,547,476; 4,548,915;4,562,173; 4,728,705; 4,816,433 4,829,037; 4,927,797; 4,990,479;5,028,671; 5,034,361; 5,066,737; 5,066,738 5,077,357; 5,082,907;5,106,806; 5,146,028; 5,151,399; 5,153,158; 5,229,342; 5,247,031;5,247,032 and 5,432,244.

Catalyst compositions designed primarily for the polymerization ofpropylene or mixtures of propylene and ethylene generally include a SCAin order to affect polymer properties, especially tacticity orstereoregularity of the polymer backbone, As one indication of the levelof tacticity, especially the isotacticity of polypropylene, the quantityof such polymer that is soluble in xylene, trichlorobenzene (TCB), orsimilar liquid that is a non-solvent for the tactic polymer is oftenused. The quantity of such polymer that is soluble in xylene is referredto as xylene solubles content or XS. In addition to tacticity control,molecular weight distribution (MWD), melt flow (MF). and otherproperties of the resulting polymer are affected by use of a SCA as wellIt has also been observed that the activity of the catalyst compositionas a function of temperature may be affected by the choice of SCA. Oftenhowever, a SCA which gives desirable control over one polymer property.Is ineffective or detrimental with respect to additional properties orfeatures. Conversely, an SCA that is effective in combination with oneprocatalyst may not be effective when used in combination with adifferent procatalyst,

With regard to the temperature dependence of catalyst activity, it isknown that the use of certain alkoxy derivatives of aromatic carboxylicacid esters, especially ethyl p-ethoxybenzoate (PEEB), in combinationwith a Ziegler-Natta procatalyst composition containing an ester of anaromatic monocarboxylic acid, exemplified by ethyl benzoate, results Inan inherently self-extinguishing catalyst composition with respect totemperature. That is, such compositions, are less active at moderatelyelevated polymerization temperatures, especially temperatures from about100° to 130° C. Using such compositions, less reactor fouling orsheeting is observed, and run-away reactors due to increasedpolymerization rates at elevated temperatures, are largely eliminated.Disadvantageously, the combination of PEEB with a procatalyst containinga dialkylester of an aromatic dicarboxylic acid, such asdiisobutylphthalate (DIBP) as an internal electron donor generallyresults in poor polymerization activity and production of polypropylenepolymers having low isotacticity (high XS).

In contrast alkoxysilane SCA's, exemplified bydicyclopentyldimethoxysilane (DCPDMS), methylcyclohexyldimethoxysilane(MChDMS) and n-propyltrimethoxysilane (NPTMS) generally are veryefficient in forming isotactic polymers having improved physicalproperties, when used in combination with a dialkyl ester of an aromaticdicarboxyiic acid, such as DIBP, as an internal electron donor.Disadvantageously however, these catalyst compositions are not generallyself-extinguishing, thereby resulting in polymerization process controlproblems due, it is believed, to localized temperature excursions. Forexample, the polymerization activity of a typical catalyst compositioncontaining DIBP as internal electron donor with an alkoxysilane as SCAgenerally increases as polymerization temperatures rise, especially attemperatures from 50° to 120° C., such, that a significant level ofcatalyst activity may remain at reaction temperatures that are close tothe softening temperature of the polymer generated.

Use of mixtures of SCA's in order to adjust polymer properties is known.Examples of prior art disclosures of catalyst compositions making use ofmixed SCA's, especially mixtures of silane or alkoxysilane SCA'sinclude; U.S. Pat Nos. 5,100,981, 5,192,732, 5,414,063, 5,432,244,5,652,303, 5,844,046, 5,849,654, 5,869,418, 6,066,702, 6,087,459,6,096,844, 6,111,039, 6,127,303, 6,133,385, 6,147,024, 6,184,328,6,303,698, 6,337,377, WO 95/21203, WO 99/20663, and WO 99/58585,Additional pertinent references include: U.S. Pat. Nos. 5,432,244,5,414,063, JP61/203,105, and EP-A-490,451.

Despite the advances occasioned by the foregoing disclosures, thereremains a need in the art to provide an aromatic dicarboxyiic acid esterinternal electron donor containing Ziegler-Natta catalyst compositionfor the polymerization of olefins, wherein the catalyst compositionretains the advantages of alkoxysilane SCA containing catalystcompositions with regard to polymer properties but additionallypossesses improved temperature/activity properties. Especially desiredare such compositions that are inherently self-extinguishing with regardto catalyst activity as a function of temperature, thereby leading toreduced polymer agglomerate formation and improved polymerizationprocess control without imparting an undesired odor to the polymer.

SUMMARY OF THE INVENTION

The present invention provides a catalyst composition for thepolymerization of propylene or mixtures of propylene and one or morecopolymerizable comonomers, said catalyst composition comprising one ormore Ziegler-Natta procatalyst compositions comprising one or moretransition metal compounds and one or more esters of aromaticdicarboxylic acid internal electron donors; one or more aluminumcontaining cocatalysts; a selectivity control agent (SCA) comprising atleast one silicon containing compound containing at least one C₁₋₁₀alkoxy group bonded to a silicon atom; and one or more activity limitingagent (ALA) compounds comprising one or more aliphatic or cycloaliphaticmono- or poly-carboxylic acids; alkyl-, aryl-, or cycloalkyl-(poly)ester derivatives thereof: or inertly substituted derivatives ofthe foregoing, said ALA compounds and amounts being selected such thatthe normalized polymerization activity of the catalyst composition at atemperature from 85° to 130° C., preferably from 100° C., to 120° C.,and more preferably at 100° C., is less than the normalizedpolymerization activity of the catalyst composition in the presence ofonly the SCA compound at the same total molar quantity of SCA at saidtemperature.

Highly preferably, the normalized polymerization activity of the SCA/ALAcombination at all temperatures from 85° to 130° C. is less than thenormalized polymerization activity of the catalyst composition in thepresence of only the alkoxysilane SCA compound at the same total molarquantity of SCA at said temperatures. Additionally or alternatively, itis desired that the normalized polymerization activity at a temperaturefrom 85° to 130° C., preferably from 100° to 120° C., most preferably at100° C., be less than the polymerization activity of the same catalystcomposition at a lesser temperature, preferably 67° C. Most preferably,more than one of the foregoing conditions regarding normalized activityare met, and most highly preferably all of the foregoing conditionsregarding normalized activity are met.

The present invention also provides a method of polymerizing propyleneor mixtures of propylene and one or more copolymerizable comonomersunder polymerization conditions using the previously describedZiegler-Natta catalyst composition comprising said mixture of SCA andALA compounds. More particularly, the process comprises contactingpropylene or a mixture of propylene and one or more copolymerizablecomonomers under polymerization conditions at a temperature from 40° to130° C., preferably from 50° to 120° C., more preferably from 60° to100° C., with a catalyst composition comprising one or moreZiegler-Natta procatalyst compositions comprising one or more transitionmetal compounds and one or more internal electron donors selected fromthe group consisting of esters of aromatic dicarboxylic acids; one ormore aluminum containing cocatalysts; a selectivity control agent (SCA)comprising at least one silicon containing compound containing at leastone C₁₋₁₀ alkoxy group bonded to a silicon atom; and from one or moreactivity limiting agent (ALA) compounds comprising one or more aliphaticor cycloaliphatic mono- or poly- carboxylic acids; alkyl-, aryl- orcycloalkyl- (poly)ester derivatives thereof; or inertly substitutedderivatives of the foregoing, said ALA compounds and amounts beingselected such that the normalized polymerization activity of thecatalyst composition at a temperature from 85° to 130° C., preferablyfrom 100° C. to 120°C., and more preferably at 100° C., is less than thenormalized polymerization activity of the catalyst composition in thepresence of only the SCA compound at the same total molar quantity ofSCA at said temperature. Additionally or alternatively, it is desired,that the normalized polymerization activity of the catalyst compositionat a temperature of 100° C. or greater, be less than the polymerizationactivity of the same catalyst composition at a lesser temperature,preferably 67° C. Most preferably both of the foregoing conditionsregarding normalized activity are met.

Highly desirably, the polymerization is conducted under conditions oftemperature and SCA/ALA content such that no substantial polymeragglomerates are formed in the polymer product and sheeting or foulingof the reactor surfaces is reduced, and most preferably, eliminated.

Although a broad range of compounds are known generally as selectivitycontrol agents, a particular catalyst composition may have a specificcompound or group of compounds with which it is especially compatible.The present invention provides a catalyst composition for thepolymerization of propylene or mixtures of propylene and one or morecopolymerizable comonomers which is especially useful with Ziegler-Nattaprocatalyst compositions formed by halogenations of mixed alkoxide metalcompounds. As a result of the present inventors discovery, it has beenunexpectedly discovered that in the foregoing operating range of mixedSCA's the advantages of using an alkoxysilane in combination with anaromatic dicarboxylic acid ester internal electron donor can be largelyretained while simultaneously improving the self-extinguishingproperties of the polymerization catalyst. Outside of the foregoing andfollowing ranges of components, this result is not observed.

DETAILED DESCRIPTION

All reference to the Periodic Table of the Elements herein shall referto the Periodic Table of the Elements, published and copyrighted by CRCPress, Inc., 2001. Also, any reference to a Group or Groups shall be tothe Group or Groups as reflected in this Periodic Table of the Elementsusing the IUPAC system for numbering groups. Tor purposes of UnitedStates patent practice, the contents of any patent, patent application,or publication referenced herein are hereby incorporated by reference intheir entirety (or the equivalent US version thereof is so incorporatedby reference) especially with respect to the disclosure of synthetictechniques, raw materials, and general knowledge in the art. Unlessstated to the contrary, implicit from the context, or customary in theart, all parts and percents are based on weight.

If appearing herein, the term “comprising” and derivatives thereof isnot intended to exclude the presence of any additional component, stepor procedure, whether or not the same is disclosed herein. In order toavoid any doubt, all compositions claimed herein through use of the term“comprising” may include any additional additive, adjuvant, or compound,unless stated to the contrary. In contrast, the term, “consistingessentially of” if appearing herein, excludes from the scope of anysucceeding recitation any other component, step or procedure, exceptingthose that are not essential to operability. The term “consisting of”,if used, excludes any component, step or procedure not specificallydelineated or listed. The term “or”, unless stated otherwise, refers tothe listed members individually as well as in any combination.

As used herein, the term “(poly)” means optionally more than one, orstated alternatively, one or more. By the term, “aliphatic orcycloaliphatic mono- or polycarboxylic acid” is meant a compoundcontaining at least one carboxylic acid group whose carbon atom isbonded to a carbon atom that is not part, of an aromatic ring system.The term “aromatic” refers to a polyatomic, cyclic, ring systemcontaining (4δ+2)π electrons, wherein 5 is an integer greater than orequal to 1. The term “inert” or “inertly substituted” as used hereinrefers to groups or substituents that do not further interact with anyother components or reagents used in the polymerization process or thatdo not interact in a manner that is significantly detrimental to thedesired polymerization process.

Unless stated to the contrary or conventional in the art, all parts andpercents used herein are based on weight. The term “equivalent percent”is based on equivalents of ALA, which is mols of ALA multiplied by thenumber of carboxylate groups per molecule and equivalents of silanecompound, which is mols of SCA multiplied by the number of silicon atomsthat are bonded to one or more alkoxy groups per molecule respectively.The term, “mixture” when used with respect to SCA's, means the use oftwo or more SCA components, simultaneously during at least a portion ofa polymerization. The individual SCA's may be added separately to areactor or premixed and added to the reactor in the form of the desiredmixture. In addition, other components of the polymerization mixture,including the procatalyst, may be combined with one or more of the SCA'sof the mixture, and/or the procatalyst, cocatalyst and a portion of themonomer optionally prepolymerized, prior to addition to the reactor. Ifmultiple reactors are employed in a polymerization wherein the presentSCA/ALA mixture is utilized, it is to be understood that differentindividual components of the SCA and ALA may be employed in eitherreactor and that the present mixture need not be employed in allreactors of the multiple reactor train.

The benefits of the invention are obtained by operation in a range ofavailability of alkoxysilane compound, such that desirable polymerproperties exemplified by melt flow, molecular weight distribution,and/or xylene solubles content, especially MF, are obtained whilesubstantially reducing the polymerization activity of the catalystcomposition at elevated reactor temperatures, especially reactortemperatures from 85° to 130° C., preferably from 100° to 120° C., dueto the presence of the ALA.

As a standardized measure of polymerization activity at elevatedtemperatures for use herein, catalyst activities are adjusted tocompensate for different monomer concentrations due to temperature. Forexample, if liquid phase (slurry or solution) polymerization conditionsare used, a correction factor to account for reduced propylenesolubility in the reaction mixture at elevated temperatures is included.That is, the catalyst activity is “normalized” due to the decreasedsolubility compared to the lower temperature, especially a 67° C.standard. The “normalized” activity, or A_(T), at temperature T, isdefined as the measured activity or (weight polymer/weight catalyst/hr)at temperature T, multiplied by a concentration correction factor,[P(67)]/[P(T)]5 where [P(67)] is the propylene concentration at 67° C.and [P(T)] is the propylene concentration at temperature T. Thecorrection factor assumes that polymerization activity increaseslinearly with propylene, concentration under the conditions employed.The correction factor is a function of the solvent or diluent used. Forexample, the empirically derived propylene correction factors at 67°,85°, 100°, 115°, 130 and 145° C. for a common C₆₋₁₀ aliphatichydrocarbon mixture (Isopar™ E, available from Exxon Chemical Company)are 1.00, 1.42, 1.93, 2.39, 2.98 and 3.70 respectively. Under gas phasepolymerization conditions, monomer solubility is normally not a factorand activity is generally uncorrected for temperature difference. Thatis, activity and normalized activity are the same.

The “normalized activity ratio” is defined as A_(T)/A₆₇, where A_(T) isthe activity at temperature T and A₆₇ is the activity at 67° C. Thisvalue can be used as an indicator of activity change as a function oftemperature. For example, an A₁₀₀/A₆₇ equal to 0.30 shows that thecatalyst activity at 100° C. is only 30 percent of the catalyst activityat 67′C.

It is to be understood that the present invention is not limited to theuse of any particular polymerization conditions in practice. In fact,the invention is particularly beneficial when employed under gas phasepolymerization conditions, in as much as control of reaction temperatureand prevention of polymer agglomeration is especially critical in a gasphase polymerization.

Suitable alkoxysilanes for use in the mixture of SCA's herein arecompounds having the general formula: SiR_(m)(OR′)_(4-m) (I) where Rindependently each occurrence is hydrogen or a hydrocarbyl or an aminogroup optionally substituted with one or more substituents containingone or more Group 14, 15, 16, or 17 heteroatoms, said R containing up to20 atoms not counting hydrogen and halogen: R′ is a C₁₋₂₀ alkyl group;and m is 0, 1, 2or 3, Preferably, R is C₆₋₁₂ aryl, alkyl or aralkyl,C₃₋₁₂ cycloallyl, C₃₋₁₂ branched alkyl, or C₃₋₁₂ cyclic amino group, R′is C₁₋₄ allyl, and m is 1 or 2. Examples of alkoxysilane selectivitycontrol agents for use herein include: dicyclopentyldimethoxysilane,di-tert-butyldimethoxysilane, methylcyclohexyldimethoxysilane,ethylcyclohexyldimethoxysilane, diphenyldimethoxysilane,diisopropyldimethoxysilane, di-n-propyldimethoxysilane,diisobutyldimethoxysilane, di-n-butyldmiethoxysilane,cyclopentyltrimethoxysilane, isopropyltrimethoxysilane,n-propyltrirnethoxysilane, n-propyltriethoxysilane,ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane,cyclopentylpyrrolidinodimethoxysilane, bis(pyrrolidino)dimethoxysilane,and bis(perhydroisoquinolino)dimethoxysilane. Preferred alkoxy silanesare dicyclopentyldimethoxysilane, methylcyclohexyldimethoxysilane, andn-propyltrimethoxysilane.

Suitable ALA compounds include aliphatic and cycloaliphaticmonocarboxylic and polycarboxylic acids containing from 2 to 50 carbons,C₁₋₅₀ alkyl-, C₆₋₅₀ aryl- or C₃₋₅₀ cycloalkyl-esters or polyesters ofaliphatic and cycloaliphatic mono- and poly- carboxylic acids containingfrom 3 to 500 carbon atoms in total, inertly substituted derivativesthereof, and mixtures of the foregoing. Suitable inert substituentsinclude aliphatic, cycloaliphatic, and aromatic substituents optionallycontaining one or more heteroatoms from Groups 14-17 of the Periodicfable of the Elements, Examples of such substituents include halo,allyl, alkenyl, cycloalkyl, aryl, alkaryl, aralkyl, (poly)alkylether,cycloalkylether, arylether, aralkylether, alkarylether, alkylthioether,arylthioether, dialkylamine, diarylamine, diaralkylamine, trialkylsilyl,(trialkylsilyl)alkyl, carboxylic acid, carboxylic acid ester, polyvalentderivatives of the foregoing, and mixtures thereof.

Desirable aliphatic or cycloaliphatic carboxylic acids, esters andpolyesters for use herein are those compounds having the formula:A³(A¹C(O)OA²)_(n)A⁴ A⁵[(A¹C(O)OA²)_(n)A⁴]_(r),[A³(A¹C(O)OA²)_(n′)]_(r′)A⁶ A⁵[(A¹C(O)OA²)_(n)A⁶]_(r), or[A⁵(A¹C(O)OA²)_(n′)]_(r′)A⁶

wherein:

A¹ independently each occurrence is a divalent aliphatic orcycloaliphatic group, a mixture thereof or a covalent bond;

A² independently each occurrence is a divalent aliphatic, cycloaliphaticor aromatic group, a mixture thereof, or a covalent bond;

A³ and A⁴ independently each occurrence are monovalent monoatomic orpolyatomic groups;

A⁵ and A⁶ independently each occurrence are covalent bonds or polyvalentmonoatomic or polyatomic groups;

r and r′ are independently each occurrence numbers from 1 to 12,preferably 1, 2or 3;

n and n′ are independently each occurrence numbers from 1 to 50,preferably from 1 to 5;

with the proviso that if A¹ is a covalent bond, then any A³ or A⁵ towhich said covalent bond is attached is aliphatic, cycloaliphatic or amixture thereof

Preferred are C₁₋₂₀ alkyl esters of aliphatic mono- and dicarboxyiicacids wherein the alkyl group is unsubstituted or substituted with oneor more Group 14, 15 or 16 heteroatom containing substituents, morepreferred are C₁₋₄ allyl mono- and diesters of aliphatic C₄₋₂₀monocarboxylic acids and dicarboxyiic acids, especially C₁₋₄ alkylesters of aliphatic C₈₋₂₀ monocarboxylic acids and dicarboxyiic acids,and C₂₋₂₀ alkyl mono- or polycarboxylate derivatives of C₂₋₁₀₀(poly)glycols or C₂₋₁₀₀ (poly)glycol ethers. Especially preferred ALA'sinclude ethyl acetate, methyl trimethylacetate, isopropyl myristate,di-n-butyl sebacate, (poly)(alkylene glycol) mono- or diacetates,(poly)(alkylene glycol) mono- or di-myristates, (poly)(alkylene glycol)mono- or di-laurates, (poly)(alkylene glycol) mono- or di-oleates,glyceryl tri(acetate), and mixtures thereof.

An especially preferred combination of SCA/ALA components is a mixtureof an alkoxy silane selected from the group consisting ofdicyclopentyldimethoxysilane, methylcyclohexyl-dimethoxysilane, andn-propyltrimethoxysilane with an ester which is isopropyl myristate,di(n-butyl) sebacate, (poly)(ethylene glycol) monolaurate, (poly)(alkeneglycol) dioleate, (poly)(ethylene glycol) methyl ether laurate, glyceryltri(acetate), or a mixture thereof.

Preferred SCA/ALA mixtures according to the invention are thosecomprising from 1 to 99.9, more preferably from 30 to 99, and mostpreferably from 50 to 98 equivalent percent of one or more ALAcompounds, and correspondingly from 99 to 0.1, more preferably from 70to 1, most preferably from 50 to 2 equivalent percent of one or morealkoxysilane compounds. Regardless of the foregoing range of components,it is to be understood by the skilled artisan that the normalizedpolymerization activity at an elevated temperature should be less thanthat obtainable at 67° C. and less than that obtainable if thealkoxysilane alone were employed alone in the same total SCA molaramount.

The total molar quantity of the SCA mixture employed in the presentinvention based on moles of transition metal is desirably from 0.1 to500, more desirably from 0.5 to 100 and most preferably from 1.0 to 50.With respect to quantity of ALA, the corresponding molar ratio based ontransition metal is desirably from 1 to 10,000, preferably from 2 to1000, and most preferably from 5 to 100.

Ziegler-Natta procatalysts for use in the present invention comprise asolid complex derived from a transition metal compound, for example,titanium-, zirconium-, chromium- or vanadium-hydrocarbyloxides,hydrocarbyls, halides, or mixtures thereof; and a Group 2 metalcompound, especially a magnesium halide, Preferred precursors comprise amixture of titanium halides supported on magnesium halide compounds.

Any of the conventional Ziegler-Natta, transition metal compoundcontaining procatalysts can be used in the present invention. Theprocatalyst component of a conventional Ziegler-Natta catalystpreferably contains a transition metal compound of the general formulaTrX_(x) where Tr is the transition metal, X is a halogen or a C₁₋₁₀hydrocarboxyl or hydrocarbyl group, and x is the number of such X groupsin the compound in combination with the foregoing Group 2 metalcompound. Preferably, Tr is a Group 4, 5or 6 metal, more preferably aGroup 4 metal, and most preferably titanium. Preferably, X is chloride,bromide, C₁₋₄ alkoxide or phenoxide, or a mixture thereof, morepreferably chloride.

Illustrative examples of suitable transition metal compounds that may beused to form a Ziegler-Natta procatalyst are TiCl₄, ZrCl₄, TiBr₄, TiCl₃,Ti(OC₂H₅)₃Cl, Zr(OC₂H₅)₃C, Ti(OC₂H₅)₃Br, Ti(OC₃H₇)₂Cl₂, Ti(OC₆H₅)₂Cl₂,Zr(OC₂H₅)₂Cl₂, and Ti(OC₂H₅)Cl3. Mixtures of such transition metalcompounds may be used as well. No restriction on the number oftransition metal compounds is made as long as at least one transitionmetal compound is present. A preferred transition metal compound is atitanium compound.

Examples of suitable Group 2 metal compounds include magnesium halides,dialkoxymagnesiums, alkoxymagnesium halides, magnesium oxyhalides,dialkylmagnesiums, magnesium oxide, magnesium hydroxide, andcarboxylates of magnesium. A most preferred Group 2 metal compound ismagnesium dichloride.

Highly desirably, the procatalysts employed in the invention are derivedfrom magnesium compounds. Examples include anhydrous magnesium chloride,magnesium chloride adducts, magnesium dialkoxides or aryloxides, orcarboxylated magnesium dialkoxides or aryloxides. Preferred compoundsare magnesium di(C₁₋₄)alkoxides, especially diethoxymagnesium.Additionally the procatalysts desirably comprise titanium moieties.Suitable sources of titanium moieties include titanium alkoxides,titanium aryloxides, and/or titanium halides. Preferred compounds usedto prepare the procatalysts comprise one or moremagnesium-di(C₁₋₄)alkoxides, magnesium dihalides,magnesiumalkoxyhalides, or mixtures thereof and one or more titaniumtetra(C₁₋₄) alkoxides, titanium tetrahalides, titanium(C₁₋₄)alkoxyhalides, or mixtures thereof.

Various methods of making precursor compounds used to prepare thepresent procatalysts are known in the art. These methods are describedin U.S. Pat. Nos. 5,034,361; 5,082,907; 5,151,399; 5,229,342; 5,106,806;5,146,028; 5,066,737; 5,077,357; 4,442,276; 4,540,679; 4,547,476;4,460,701; 4,816,433; 4,829,037; 4,927,797; 4,990,479; 5,066,738;5,028,671; 5,153,158; 5,247,031; 5,247,032, and elsewhere. In apreferred method, the preparation involves chlorination of the foregoingmixed magnesium compounds, titanium compounds, or mixtures thereof, andmay involve the use of one or more compounds, referred to as “clippingagents”, that aid in forming or solubilizing specific compositions via asolid/solid metathesis. Examples of suitable clipping agents includetrialkylborates, especially triethylborate, phenolic compounds,especially cresol, and silanes.

A preferred precursor for use herein is a mixed magnesium/titaniumcompound of the formula Mg_(d)Ti(OR^(e))_(e)X_(f) wherein R^(e) is analiphatic or aromatic hydrocarbon radical having 1 to 14 carbon atoms orCOR′ wherein R′ is an aliphatic or aromatic hydrocarbon radical having 1to 14 carbon atoms; each OR³ group is the same or different; X isindependently chlorine, bromine or iodine; d is 0.5 to 5. preferably2-4, most preferably 3; e is 2-12, preferably 6-10, most preferably 8;and f is 1-10, preferably 1-3, most preferably 2. The precursors areideally prepared by controlled precipitation through removal of analcohol from the reaction mixture used in their preparation. Anespecially desirable reaction medium comprises a mixture of an aromaticliquid, especially a chlorinated aromatic compound, most especiallychlorobenzene, with an alkanol, especially ethanol, and an inorganicchlorinating agent. Suitable inorganic chlorinating agents includechlorine derivatives of silicon, aluminum and titanium, especiallytitanium tetrachloride or titanium trichloride, most especially titaniumtetrachloride. Removal of the alkanol from the solution, used in thechlorination, results in precipitation of the solid precursor, havingespecially desirable morphology and surface area. Moreover, theresulting precursors are particularly uniform particle sized andresistant to particle crumbling as well as degradation of the resultingprocatalyst.

The precursor is next converted to a solid procatalyst by furtherreaction (halogenation) with an inorganic halide compound, preferably atitanium halide compound, and incorporation of an internal electrondonor. If not already incorporated into the precursor in sufficientquantity, the electron donor may be added separately before, during orafter halogenation. This procedure may be repeated one or more times,optionally in the presence of additional additives or adjuvants, and thefinal solid product washed with an aliphatic solvent, Any method ofmaking, recovering and storing the solid procatalyst is suitable for usein the present invention.

One suitable method for halogenation of the precursor is by reacting theprecursor at an elevated temperature with a tetravalent titanium halide,optionally in the presence of a hydrocarbon or halohydrocarbon diluent.The preferred tetravalent titanium halide is titanium tetrachloride. Theoptional hydrocarbon or halohydrocarbon solvent employed in theproduction of olefin polymerization procatalyst preferably contains upto 12 carbon atoms inclusive, more preferably up to 9 carbon atomsinclusive. Exemplary hydrocarbons include pentane, octane, benzene,toluene, xylene, alkylbenzenes, and decahydronaphthalene. Exemplaryaliphatic halohydrocarbons include methylene chloride, methylenebromide, chloroform, carbon tetrachloride, 1,2-dibromoethane,1,1,2-trichloroethane, trichlorocyclohexane, dichlorofluoromethane andtetrachlorooctane. Exemplary aromatic halohydrocarbons includechlorobenzene, bromobenzene, dichlorobenzenes and chlorotoluenes. Of thealiphatic halohydrocarbons, compounds containing at least two chloridesubstituents are preferred, with carbon tetrachloride and1,1,2-trichloroethane being most preferred. Of the aromatichalohydrocarbons, chlorobenzene and o-chlorotoluene are particularlypreferred.

The halogenation may be repeated one or more times, optionallyaccompanied by washing with an inert liquid such as an aliphatic oraromatic hydrocarbon or halohydrocarbon between halogenations andfollowing halogenation. Further optionally one or more extractionsinvolving contacting with an inert liquid diluent, especially analiphatic or aromatic hydrocarbon, especially at an elevated temperaturegreater than 100° C., preferably greater than 110° C., may be employedto remove labile species, especially TiCl₄.

Preferred Ziegler-Natta procatalysts that may be used in the presentinvention are disclosed in U.S. Pat. Nos. 4,927,797; 4,816,433 and4,839,321. In these patents procatalyst is described comprising a solidcatalyst component obtained by (i) suspending a dialkoxy magnesium in anaromatic hydrocarbon that is liquid at normal temperatures, (ii)contacting the dialkoxy magnesium with a titanium halide and further(iii) contacting the resulting composition a second time with thetitanium halide, and contacting the dialkoxy magnesium with a diester ofan aromatic dicarboxylic acid at some point during the treatment withthe titanium halide in (ii).

Preferred internal electron donors for use in the present catalystcomposition to provide tacticity control and catalyst crystallite sizingare aromatic dicarboxylic acid esters, halides or anhydrides or(poly)alkyl ether derivatives thereof, especially C₁₋₄ dialkyl esters ofphthalic or terephthalic acid, phthaloyl dichloride, phthalic anhydride,and C₁₋₄ (poly)alkyl ether derivatives thereof. A highly preferredinternal electron donor is diisobutyl phthalate or di-n-butyl phthalate.

The Ziegler-Natta, transition metal catalyst may also include an inertsupport material, if desired. The support should be an inert solid whichdoes not adversely alter the catalytic performance of the transitionmetal compound. Examples include metal oxides, such as alumina, andmetalloid oxides, such as silica.

Cocatalysts for use with the foregoing Ziegler-Natta catalysts accordingto the invention include organoaluminum compounds, such astrialkylaluminum-, dialkylaluminum hydride-, alkylaluminum dihydride-,dialkylaluminum halide-, alkylaluminumdihalide-, dialkylaluminumalkoxide-, and alkylaluminum dialkoxide-compounds containing from 1-10,preferably 1-6 carbon atoms in each alkyl- or alkoxide-group. Preferredcocatalysts are C₁₋₄ trialkylaluminum compounds, especiallytriethylaluminum (TEA).

One suitable method of practicing a polymerization process according tothe present invention comprises performing the following steps in anyorder or in any combination, or subcombination of individual steps:

a) providing a Ziegler-Natta catalyst composition to a polymerizationreactor;

b) providing an organoaluminum cocatalyst compound to the polymerizationreactor;

c) providing a SCA/ALA mixture meeting the foregoing requirements to thepolymerization reactor;

d) providing one or more polymerizable monomers to the reactor; and

e) extracting polymer product from the reactor,

In another suitable method of operation, the one or more of thepreviously identified aliphatic or cycloaliphatic, carboxylic acidesters or polyesters may be added to the reactor intermittently as ameans of controlling the polymerization activity in the reactor. In thismethod of operation, the reactor may be operated normally using only analkoxysilane SCA and when conditions conducive to the formation ofpolymer agglomerates or a run away reaction are encountered, especiallywhen polymerization temperatures exceed 80° C., more especially 100° C.,the SCA/ALA mixture of the present invention may be formed in situ, byaddition of the one or more aliphatic or cycloaliphatic, carboxylic acidesters or polyesters to the reactor contents for a time sufficient toreduce polymer agglomeration, sheeting, or fouling or to otherwisestabilize the polymerization,

In another suitable method of operation, the procatalyst is treated withthe one or more aliphatic or cycloaliphatic, carboxylic acid esters orpolyesters (first ALA component) in the presence of the aluminumcompound cocatalyst. The resulting composition may be stored and shippedprior to use or used directly in a polymerization reaction according tothe invention by combining the same with one or more alkoxysilanes (SCAcomponent), optionally in combination with additional quantities of oneor more aliphatic or cycloaliphatic, carboxylic acid ester or polyestercompounds. In this embodiment, trialkylaluminum compounds are preferredcocatalysts.

In another suitable method of operation, the procatalyst may be treatedwith the alkoxysilane SCA component, optionally in the presence of analuminum cocatalyst compound. The resulting composition may also bestored and shipped prior to use or used directly in a polymerizationreaction according to the invention wherein only the ALA component isseparately added, optionally in combination with additional quantitiesof one or more alkoxysilane(s). In this embodiment as well,trialkylaluminum compounds are preferred cocatalysts.

In a final embodiment, it has been discovered that improved polymerproperties and activity is obtained if the alkoxysilane is contacted(precontacted) with an organoaluminum compound, preferably in at least astoichiometric quantity, prior to contacting with the ALA compound and,further preferably, prior to contacting with the procatalystcomposition. Highly preferably from 0.1 to 500 moles, most preferablyfrom 1.0 to 100 moles of organoaluminum compound are employed per moleof alkoxysilane. Suitable organoaluminum compounds include thecocatalyst employed in the formation of the polymerization catalyst or aportion thereof. Preferred organoaluminum compounds are trialkylaluminumcompounds containing from 1 to 8 carbons in each alkyl group, mostpreferably, triethylaluminum (TEA).

The catalyst composition of the invention may be used in most allcommercially known polymerization processes, including thoseincorporating a pre-polymerization step, whereby a small amount ofmonomer is contacted with the catalyst after the catalyst has beencontacted with the co-catalyst and the selectivity control agent mixtureor individual components thereof. Then, the resulting preactivatedcatalyst stream is introduced into the polymerization reaction zone andcontacted with the remainder of the monomer to be polymerized, andoptionally one or more of the SCA and ALA components. When used, thisresults in the procatalyst additionally comprising one or morealkoxysilane compounds and an aluminum alkyl compound and the catalystcomposition is prepared by combining the same with one or more ALAcompounds, optionally in combination with additional quantities of oneor more alkoxysilane compounds and/or one or more cocatalysts.

Preferred polymerization processes in which the present invention isparticularly suited include gas phase, slurry, and bulk polymerizationprocesses, operating in one or more than one reactor. Suitable gas phasepolymerization processes include the use of condensing mode as well assuper condensing mode wherein gaseous components including added inertlow boiling compounds are injected into the reactor in liquid form forpurposes of heat removal. Best results are obtained, especially whenoperating in the gas phase, at lower cocatalyst/SCA ratios. Whenmultiple reactors are employed it is desirable that they operate inseries, that is the effluent from the first reactor is charged to thesecond reactor and additional monomer or different monomer added tocontinue polymerization. Additional catalyst or catalyst components(that is procatalyst or cocatalyst) may be added, as well as additionalquantities of the SCA/ALA mixture, another SCA mixture, or individualSCA or ALA compounds comprising the present SCA/ALA mixture. Highlydesirably, the SCA/ALA mixture of the invention is added to only thefirst reactor of the series.

More preferably, the process of the invention is conducted in tworeactors in which two olefins, most preferably, propylene and ethylene,are contacted to prepare a copolymer. In one such process, polypropyleneis prepared in the first reactor and a copolymer of ethylene andpropylene is prepared in the second reactor in the presence of thepolypropylene prepared in the first reactor. Regardless of thepolymerization technique employed, it is understood that the SCA/ALAmixture and the catalyst composition to be employed, or at least theprocatalyst component thereof may be contacted in the absence of otherpolymerization components, especially monomer, prior to addition to thereactor. In a preferred embodiment, the foregoing dual polymerizationprocesses are solution polymerizations.

Suitably, the polymerization in which the present SCA/ALA mixture isemployed is conducted at temperatures from 40° to 130° C., morepreferably from 60° to 100° C. The foregoing temperatures are averagetemperatures of the reaction mixture measured at the reactor walls.Isolated regions of the reactor may experience localized temperaturesthat exceed the foregoing limits.

The following embodiments of the invention are provided as specificenablement for the appended claims. Accordingly, the present inventionprovides:

1. A catalyst composition for the polymerization of propylene ormixtures of propylene and one or more copolymerizable comonomers, saidcatalyst composition comprising one or more Ziegler-Natta procatalystcompositions comprising one or more transition metal compounds and oneor more esters of aromatic dicarboxyiic acid internal electron donors;one or more aluminum containing cocatalysts; a selectivity control agent(SCA) comprising at least one silicon containing compound containing atleast one C₁₋₁₀ alkoxy group bonded to a silicon atom: and one or moreactivity limiting agent (ALA) compounds comprising one or more aliphaticor cycloaliphatic mono- or poly- carboxylic acids; alkyl-, aryl-, orcycloalkyl-(poly)ester derivatives thereof; or inertly substitutedderivatives of the foregoing, said ALA compounds and amounts beingselected such that the normalized polymerization activity of thecatalyst composition at a temperature from 85° to 130° C., preferablyfrom 100° C. to 120° C., and more preferably at 100° C., is less thanthe normalized polymerization activity of the catalyst composition in.the presence of only the SCA compound at the same total molar quantityof SCA at said temperature.

2. A catalyst composition for the polymerization of propylene ormixtures of propylene and one or more copolymerizable comonomers, saidcatalyst composition comprising one or more Ziegler-Natta procatalystcompositions comprising one or more transition metal compounds and oneor more esters of aromatic dicarboxyiic acid internal electron donors;one or more aluminum containing cocatalysts; a selectivity control agent(SCA) comprising at least one silicon containing compound containing atleast one C₁₋₁₀ alkoxy group bonded to a silicon atom; and one or moreactivity limiting agent (ALA) compounds comprising one or more aliphaticor cycloaliphatic mono- or poly- carboxylic acids; alkyl-, aryl-, orcycloalkyl-(poly)ester derivatives thereof; or inertly substitutedderivatives of the foregoing, said compounds and amounts being selectedsuch that the normalized polymerization activity of the catalystcomposition at a temperature from 85° C. to 130° C., is less than thenormalized polymerization activity of the same catalyst composition andthe SCA/ALA mixture at a lesser temperature.

3. A catalyst composition for the polymerization of propylene ormixtures of propylene and one or more copolymerizable comonomers, saidcatalyst composition comprising one or more Ziegler-Natta procatalystcompositions comprising one or more transition metal compounds and oneor more esters of aromatic dicarboxylic acid internal electron donors;one or more aluminum containing cocatalysts: a selectivity control agent(SCA) comprising at least one silicon containing compound containing atleast one C₁₋₁₀ alkoxy group bonded to a silicon atom; and one or moreactivity limiting agent (ALA) compounds comprising one or more aliphaticor cycloaliphatic mono- or poly- carboxylic acids; alkyl-, aryl-, orcycloalkyl-(poly)ester derivatives thereof, or inertly substitutedderivatives of the foregoing, said compounds and mounts being selectedsuch that the normalized polymerization activity of the catalystcomposition at a temperature from 85° C. to 130° C. is less than thenormalized polymerization activity of the catalyst composition in thepresence of only the SCA compound at the same total molar quantity ofSCA at said temperature, and also less than the polymerization activityof the same catalyst composition and SCA/ALA mixture at a lessertemperature.

4. A catalyst composition according to any one of embodiments 1-3wherein the total quantity of selectivity control agent employed islimited to provide a molar ratio, based on transition metal, from 0.1 to500.

5. A catalyst composition according to any one of embodiments 2 to 3wherein the lesser temperature is 67° C.

6. A catalyst composition according to embodiment 4 wherein the SCA/ALAequivalent ratio is from 99/1 to 0.1/99.9.

7. A catalyst composition according to embodiment 4 wherein the SCA is acompound having the general formula: SiR_(m)(OR′)_(4-m) (I) where Rindependently each occurrence is hydrogen or a hydrocarbyl groupoptionally substituted with one or more substituents containing one ormore Group 14-17 heteroatoms, said R containing up to 20 atoms notcounting hydrogen or halogen; R′ is a C₁₋₂₀ alkyl group; and m is 0, 1,2 or 3 and the ALA is selected from aliphatic or cycloaliphaticcarboxylic acid-, ester- and poly-ester-compounds having the formula:A³(A¹C(O)OA²)_(n)A⁴ A⁵[(A¹C(O)OA²)_(n)A⁴]_(r),[A³(A¹C(O)OA²)_(n′)]_(r′)A⁶ A⁵[(A¹C(O)OA²)_(n)A⁶]_(r), or[A⁵(A¹C(O)OA²)_(n′)]_(r′)A⁶

wherein

A¹ independently each occurrence is a divalent aliphatic orcycloaliphatic group, a mixture thereof, or a covalent bond;

A² independently each occurrence is a divalent aliphatic, cycloaliphaticor aromatic group, a mixture thereof, or a covalent bond;

A³ and A⁴ independently each occurrence are monovalent monoatomic orpolyatomic groups;

A⁵ and A⁶ independently each occurrence are covalent bonds or polyvalentmonoatomic or polyatomic groups;

r and r′ are independently each occurrence numbers from 1 to 12,preferably 1, 2or 3;

n and n′ are independently each occurrence numbers from 1 to 50,preferably from 1 to 5;

with the proviso that if A¹ is a covalent bond, then any A³ or A⁵ towhich said covalent bond is attached is aliphatic, cycloaliphatic or amixture thereof.

8. A catalyst composition according to embodiment 7 wherein theselectivity control agent is selected from the group consisting of:dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane,methylcyclohexyldimethoxysilane, ethylcyclohexyldimethoxysilane,diphenyldimethoxysilane, diisopropyldimethoxysilane,di-n-propyldimethoxysilane, diisobutyldimethoxysilane,di-n-butyldimethoxysilane, cyclopentyltrimethoxysilane,isopropyltrimethoxysilane, n-propyltrimethoxysilane,n-propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane,tetraethoxysilane, cyclopentylpyrrolidinodimethoxysilane,bis(pyrrolidino)-dimethoxysilane, andbis(perhydroisoquinolino)dimethoxysilane and the ALA is selected fromthe group consisting of: ethyl acetate, methyl trimethylacetate,isopropyl myristate, di-n-butyl sebacate, (poly)(alkylene glycol) mono-or diacetates, (poly)(alkylene glycol) mono- or di-myristates,(poly)(alkylene glycol) mono- or di-laurates, (poly)(alkylene glycol)mono- or di-oleates, glyceryl tri(acetate), mixed glycerides oflinoleic, oleic, palmitic and stearic acids, and mixtures thereof.

9. A catalyst composition according to embodiment 8 wherein theselectivity control agent is selected from the group consisting of:dicyclopentyldimethoxysilane, methylcyclohexyldimethoxysilane, andn-propyltrimethoxysilane and the ALA is selected from the groupconsisting of: isopropyl myristate, di(n-butyl) sebacate,(poly)(ethylene glycol) monolaurate, (poly)(alkene glycol) dioleate,poly(ethylene glycol) methyl ether laurate, glyceryl tri(acetate), or amixture thereof.

10. A polymerization embodiment comprising contacting propylene or amixture of propylene and one or more copolymerizable comonomers underpolymerization conditions at a temperature from 40° to 130° C., with acatalyst composition according to embodiment 4.

11. A process according to embodiment 10 which is a gas phasepolymerization process.

12. A process according to embodiment 10 which is conducted in more thanone reactor operating in series.

EXAMPLES

The invention is further illustrated by the following examples thatshould not be regarded as limiting of the present invention. Unlessstated to the contrary or conventional in the art, all parts andpercents are based on weight.

A titanium containing Ziegler-Natta catalyst composition is employed toproduce polypropylene homopolymers. The catalyst composition includes aprocatalyst compound prepared by slurrying a mixture of a magnesiumdiethoxide and titanium ethoxide/chloride containing precursorcorresponding to the formula Mg₃Ti(OC₂H₅)₈Cl (made substantiallyaccording to U.S. Pat. No. 5,077,357) with diisobutylphthalate (0.2liter/kilogram precursor) in a 50/50 (vol/vol) mixture ofTiCl₄/monochlorobenzene (MCB, 19 liters/kilogram precursor). After themixture is heated at 113° C. for 60 minutes, it is filtered. Theresulting moist mass is slurried in a 50/50 TiCl₄/MCB mixture (19liters/kilogram precursor) at 113° C. for 30 minutes, filtered, and theprocess repeated once more. The resulting solid is rinsed withisopentane and then dried with flowing warm nitrogen. The resultingprocatalyst containing 2.6 percent Ti is ground and sieved prior to usein polymerizations.

Propylene polymerizations are carried out in a 48 cell automated,combinatorial multireactor (available from Symyx Technologies, Inc.)operated substantially according to the teachings of U.S. Pat. No.6,306,658. All solvents are dried prior to use. Reagents and reactorconditions employed are: an initial charge of 70 kPa (10 psig) H₂, 110μl of a 0.20M solution of triethylaluminum (TEA) in mixed alkanes(calculated to provide an Al/Ti molar ratio of 500/1), 4515 μl of mixedalkanes, propylene at a pressure of 0.7 MPa (100 psig) (suppliedcontinuously during the polymerization), 132 μl of a 0.01 M solution ofSCA mixture in mixed alkanes (calculated to give a SCA/Ti ratio of 30/1)followed by 500 μl of mixed alkanes, and 275 μl of a toluene slurry ofthe procatalyst, again followed by 500 μl of mixed alkanes.Polymerization is terminated by addition of CO₂ at the end of 3600seconds or upon sensing a preset propylene flow limit of approximately150 percent of initial charge. Upon completion of polymerization, thereactors are vented to ambient pressure; the glass vials containingpolymer are removed and devolatilized in a rotary evaporator at 25° C.for 16 hours. The polymer yields are determined by weight difference ofthe vials before and after polymerization and devolatilization.

The SCA/ALA mixtures tested include: n-propyltrimethoxysilane (NPTMS)with ethylacetate (EA), methyl trimethylacetate (MTMA), anddi(n-butyl)sebacate (DBS); dicyclopentyldimethoxysilane (DCPDMS)/withDBS; and methylcyclohexyldimethoxysilane (MChDMS)/with DBS,glyceryltriacetate (GTA), beeswax (mixed straight chain carboxylic acidesters, primarily myricyl palmitate, C₁₅H₃₁C(O)O(C₃₀H₆₁)), coconut oil(mixed glycerides of lauric, capric, myristic, palmitic and oleicacids), corn oil (mixed glycerides of linoleic, oleic, palmitic andstearic acids), Cyanox™ STDP (available from Cytee Industries, Inc.),Irganox™ 1010, Tinuvin™ 622 and Tinuvin™ 770 (all available fromCiba-Geigy Corporation).

The latter trademarked compounds have the following structural formulas:

Normalized activity (A_(T)) as well as (A_(T)/A₆₇) for the various SCAcombinations, amounts and temperatures are provided in Table 1. Allresults are the average of from two to four individual polymerizations.

TABLE 1 Monocarboxylate ALA Compounds Normalized SCA/ALA/Ti SCA/CO₂/TISCA/ALA Temp Activity, A_(t) A_(t)/A₆₇ Run SCA ALA (mol/mol/mol(mol/mol/mol (mol. %) (° C.) (kg/g/hr) (%) A1* NPTMS — 30/0/1 30/0/1100/0   67 2.95 100 A2* ″ — ″ ″ ″ 100 6.27 213 A3* ″ — ″ ″ ″ 115 1.65 56B1* — EA 0/30/1 0/30/1  0/100 67 2.23 100 B2* — ″ ″ ″ ″ 100 1.51 68 B3*— ″ ″ ″ ″ 115 0.69 31 C1* — MTMA 0/30/1 0/30/1  0/100 67 1.85 100 C2* —″ ″ ″ ″ 100 1.41 76 C3* — ″ ″ ″ ″ 115 0.79 43 1a NPTMS EA 1.2/28.2/11.2/28.2/1 4/96 67 2.67 100 1b ″ ″ ″ ″ ″ 100 0.91 34 1c ″ ″ ″ ″ ″ 1150.50 19 2a NPTMS MTMA 1.5/28.5/1 1.5/28.5/1 5/95 67 3.16 100 2b ″ ″ ″ ″″ 100 1.25 40 2c ″ ″ ″ ″ ″ 115 0.65 20 *comparative, not an example ofthe invention

As may be seen by reference to the results of Table 1, by using SCA/ALAmixtures according to the invention, reduced polymerization activity(normalized) may be obtained at elevated polymerization temperatures,compared to use of the silane SCA compound alone or compared to the useof the same SCA/ALA mixture at a lower polymerization temperature. Thereduction may be controlled by adjusting the quantities of SCA and ALAemployed, so that normalized activity levels substantially less thanthose obtainable by use of the SCA alone or less than the activity withthe same SCA/ALA mixture at 67° C., are obtainable. Those illustratedcompositions possess self-limiting polymerization properties.Accordingly, use of such SCA/ALA mixtures can reduce or avoid anuncontrolled acceleration of the reaction, as well as softening ormelting of polymer particles that leads to agglomerate formation andsheeting or fouling of the reactor, Analysis of the resulting polymersproduced from alkoxysilane containing SCA/ALA mixtures demonstrate thatthe polymers retain beneficial tacticity and molecular weightdistribution properties due to the use of the alkoxysilane SCA.

Tables 2, 3 and 4 illustrate the results of using dicarboxylic acidesters, tricarboxylic acid esters and various carboxylate compoundsrespectively.

TABLE 2 Dicarboxylate ALA Compounds Normalized SCA/ALA/Ti SCA/CO₂/TISCA/ALA Temp Activity, A_(t) A_(t)/A₆₇ Run SCA ALA (mol/mol/mol(mol/mol/mol (mol. %) (° C.) (kg/g/hr) (%) D1* MChDMS PEEB 1.5/28.5/11.5/28.5/1  5/95 67 3.16 100 D2* ″ ″ ″ ″ ″ 100 1.10 35 D3* ″ ″ ″ ″ ″ 1150.88 28 E1* NPTMS — 30/0/1 30/0/1 100/0  67 2.95 100 E2* ″ — ″ ″ ″ 1006.27 213 E3* ″ — ″ ″ ″ 115 1.65 56 F1* MChDMS — 30/0/1 30/0/1 100/0  675.75 100 F2* — ″ ″ ″ 100 4.75 83 F2* — ″ ″ ″ 115 2.15 37 G1* DCPDMS —30/0/1 30/0/1 100/0  67 5.99 100 G2* ″ — ″ ″ ″ 100 5.96 100 G3* ″ — ″ ″″ 115 3.85 64  3a MChDMS DBS 0.75/14.625/1 0.75/29.25/1  5/95 67 5.17100  3b ″ ″ ″ ″ ″ 100 0.85 16  3c ″ ″ ″ ″ ″ 115 0.53 10  4a MChDMS DBS1.5/14.25/1 1.5/28.5/1 10/90 67 7.00 100  4b ″ ″ ″ ″ ″ 100 0.89 13  4c ″″ ″ ″ ″ 115 0.84 12  5a MChDMS DBS 3/27/1 3/54/1 10/90 67 3.57 100  5b ″″ ″ ″ ″ 100 0.58 16  5c ″ ″ ″ ″ ″ 115 1.36 38  6a MChDMS DBS 6/24/16/48/1 20/80 67 4.85 100  6b ″ ″ ″ ″ ″ 100 2.78 57  6c ″ ″ ″ ″ ″ 1151.79 37  7a MChDMS DBS 9/21/1 9/42/1 30/70 67 5.69 100  7b ″ ″ ″ ″ ″ 1003.69 65  7c ″ ″ ″ ″ ″ 115 1.58 28  8a NPTMS DBS 3/27/1 3/54/1 10/90 673.35 100  8b ″ ″ ″ ″ ″ 100 0.81 24  8c ″ ″ ″ ″ ″ 115 0.62 19  9a NPTMSDBS 6/24/1 6/48/1 20/80 67 3.54 100  9b ″ ″ ″ ″ ″ 100 1.49 42  9c ″ ″ ″″ ″ 115 0.91 26 10a NPTMS DBS 9/21/1 9/42/1 30/70 67 3.85 100 10b ″ ″ ″″ ″ 100 1.60 42 10c ″ ″ ″ ″ ″ 115 0.91 24 11a DCPDMS DBS 0.75/29.25/10.75/58.5  2.5/97.5 67 3.44 100 11b ″ ″ ″ ″ ″ 100 1.33 39 11c ″ ″ ″ ″ ″115 1.24 36 12a DCPDMS DBS 1.5/28.5/1 1.5/57/1  5/95 67 4.64 100 12b ″ ″″ ″ ″ 100 1.81 39 12c ″ ″ ″ ″ ″ 115 1.86 40 13a DCPDMS DBS 3/27/1 3/54/110/90 67 4.82 100 13b ″ ″ ″ ″ ″ 100 3.65 76 13c ″ ″ ″ ″ ″ 115 2.03 42*comparative, not an example of the invention PEEB = ethylp-ethoxybenzoate

Polymer properties for polymers prepared using the foregoing SCA/ALAmixtures are analyzed and determined to be substantially the same asthose of polymers prepared using the corresponding SCA alone.

TABLE 3 Tricarboxylate ALA Compounds SLA = MChDMS Normalized SCA/ALA/TiSCA/CO₂/TI SCA/ALA Temp Activity, A_(t) A_(t)/A₆₇ Run ALA (mol/mol/mol(mol/mol/mol (mol. %) (° C.) (kg/g/hr) (%) H1* PEEB 1.5/28.5/11.5/28.5/1  5/95 67 3.16 100 H2* ″ ″ ″ ″ 100 1.10 35 H3* ″ ″ ″ ″ 1150.88 28 I1* — 30/0/1 30/0/1 100/0  67 5.75 100 I2* — ″ ″ ″ 100 4.75 83I3* — ″ ″ ″ 115 2.15 37 I4a triacetin 0.75/9.75/1 1.5/28.5/1  7/93 675.40 100 14b ″ ″ ″ ″ 100 2.10 39 14c ″ ″ ″ ″ 115 1.20 22 15a triacetin1.5/9.5/1 1.5/28.5/1 14/86 67 8.52 100 15b ″ ″ ″ ″ 100 2.43 29 15c ″ ″ ″″ 115 1.41 17 *comparative, not an example of the invention PEEB = ethylp-ethoxybenzoate, triacetin = glyceryl triacetate

Polymer properties for polymers prepared using the foregoing SCA/ALAmixtures are analyzed and determined to be substantially the same asthose of polymers prepared using the corresponding SCA alone.

TABLE 4 Mixed Carboxylate Functional Group Containing ALA Compounds SCA= MChDMS Normalized SCA/ALA/Ti SCA/CO₂/TI SCA/ALA Temp Activity, A_(t)A_(t)/A₆₇ Run ALA (mol/mol/mol (mol/mol/mol (mol. %) (° C.) (kg/g/hr)(%) J1* PEEB 1.5/28.5/1 1.5/28.5/1  5/95 67 3.16 100 J2* ″ ″ ″ ″ 1001.10 35 J3* ″ ″ ″ ″ 115 0.88 28 K1* — 30/0/1 30/0/1 100/0  67 5.75 100K2* — ″ ″ ″ 100 4.75 83 K3* — ″ ″ ″ 115 2.15 37 16a Irganox ™1.5/7.125/1 1.5/28.5/1 17/83 67 5.13 100 16b ″ ″ ″ ″ 100 2.45 48 16c ″ ″″ ″ 115 1.29 25 17a Cyanox ™ 1.5/14.25/1 1.5/28.5/1 10/90 67 6.87 10017b ″ ″ ″ ″ 100 2.01 29 17c ″ ″ ″ ″ 115 1.12 16 18a Tinuvin ™~1.5/28.5/1 67 4.20 100 622 18b Tinuvin ™ ″ 100 2.97 71 622 18cTinuvin ™ ″ 115 1.55 37 622 19a Tinuvin ™ 1.5/14.25/1 1.5/28.5/1 10/9067 2.72 100 770 19b Tinuvin ™ ″ ″ ″ 100 1.06 39 770 L1* — 30/0/1 30/0/1 0/100 67 5.75 100 L2* — ″ ″ ″ 115 2.15 37 20a beeswax ~1.5/28.5/1~1.5/28.5/1 ~5/95 67 4.65 100 20b ″ ″ ″ ″ 100 1.37 29 20c ″ ″ ″ ″ 1151.15 25 21a coconut oil 1.5/9.5/1 1.5/28.5/1 14/86 67 4.97 100 21b ″ ″ ″″ 100 2.57 52 21c ″ ″ ″ ″ 115 1.67 34 22a corn oil 1.5/9.5/1 1.5/28.5114/86 67 5.21 100 22b ″ ″ ″ ″ 100 2.70 52 22c ″ ″ ″ ″ 115 1.46 28*comparative, not an example of the invention PEEB = ethylp-ethoxybenzoate

Polymer properties for polymers prepared using the foregoing SCA/ALAmixtures at 67° C. are analyzed and determined to be substantially thesame as those of polymers prepared using the corresponding SCA alone atthe same temperature.

1. A polymerization process comprising: charging an effluent of a firstpolymerization reactor to a second polymerization reactor; contactingthe effluent with propylene and a copolymerizable comonomer underpolymerization conditions in the second polymerization reactor; adding amixture of a selectivity control agent (SCA) comprising one or moresilicon containing compounds and an activity limiting agent (ALA)selected from the group consisting of a C₁₋₂₀ alkyl ester of analiphatic C₈₋₂₀ monocarboxylic acid, a C₂₋₂₀ alkyl mono- orpoly-carboxylate derivative of a C₂₋₁₀₀ polyglycol, and combinationsthereof to the second polymerization reactor; and forming a copolymer.2. The polymerization process of claim 1 wherein the effluent comprisesa polypropylene and the copolymerizable copolymer is ethylene, theprocess comprising forming a copolymer of propylene and ethylene in thepresence of the polypropylene in the second reactor.
 3. The process ofclaim 1 comprising adding the SCA/ALA mixture to the second reactor andeliminating fouling in the second reactor.
 4. The polymerization processof claim 1 comprising mixing the ALA with the SCA before the adding. 5.The process of claim 1 comprising forming the SCA/ALA mixture in thesecond reactor in situ.
 6. The process of claim 1 comprising impartingno undesired odor to the copolymer.
 7. A polymerization processcomprising: preparing a polypropylene in a first polymerization reactor;preparing a copolymer of ethylene and propylene in the presence of thepolypropylene in a second polymerization reactor; and adding, to atleast one of the polymerization reactors, a mixture of a selectivitycontrol agent (SCA) comprising one or more silicon containing compoundsand an activity limiting agent (ALA) selected from the group consistingof a C₁₋₂₀ alkyl ester of an aliphatic C₈₋₂₀ monocarboxylic acid, aC₂₋₂₀ alkyl mono- or poly-carboxylate derivative of a C₂₋₁₀₀ polyglycol,and combinations thereof.
 8. The process of claim 7 comprising addingthe SCA/ALA mixture to a member selected from the group consisting ofthe first polymerization reactor, the second polymerization reactor, andcombinations thereof.
 9. The process of claim 7 comprising adding theSCA/ALA mixture to the second polymerization reactor.
 10. The process ofclaim 7 comprising adding a first SCA/ALA mixture to the firstpolymerization reactor and adding a second SCA/ALA mixture to the secondreactor.
 11. The process of claim 7 comprising forming, in the secondpolymerization reactor, a copolymer comprising the polypropylene and thecopolymer of ethylene and propylene.
 12. The polymerization process ofclaim 7 comprising adding a mixture comprising the SCA and an ALAselected from the group consisting of a C₁₋₂₀ alkyl ester of analiphatic C₈₋₂₀ monocarboxylic acid, a C₂₋₂₀ alkyl mono- orpoly-carboxylate derivative of a C₂₋₁₀₀ polyglycol, and combinationsthereof.
 13. The process of claim 7 comprising adding the SCA/ALAmixture to the second polymerization reactor; and eliminating fouling inthe second polymerization reactor.
 14. A polymerization processcomprising: preparing a copolymer of ethylene and propylene in thepresence of a polypropylene in a polymerization reactor underpolymerization conditions; and adding, to the polymerization reactor, amixture of a selectivity control agent (SCA) comprising one or moresilicon containing compounds and an activity limiting agent (ALA)selected from the group consisting of a C₁₋₂₀ alkyl ester of analiphatic C₈₋₂₀ monocarboxylic acid, a C₂₋₂₀ alkyl mono- orpoly-carboxylate derivative of a C₂₋₁₀₀ polyglycol, and combinationsthereof.
 15. The polymerization process of claim 14 comprising adding amixture comprising the SCA and an ALA selected from the group consistingof a C₁₋₂₀ alkyl ester of an aliphatic C₈₋₂₀ monocarboxylic acid, aC₂₋₂₀ alkyl mono- or poly-carboxylate derivative of a C₂₋₁₀₀ polyglycol,and combinations thereof.
 16. The polymerization process of claim 14comprising eliminating, with the addition of the SCA/ALA mixture,fouling in the polymerization reactor.
 17. The polymerization process ofclaim 14 comprising separately adding the ALA and separately adding theSCA to the polymerization reactor.
 18. The polymerization process ofclaim 14 comprising mixing the ALA and the SCA before the adding. 19.The polymerization process of claim 14 comprising preparing thepolypropylene in a first polymerization reactor and preparing thecopolymer of ethylene and propylene in a second polymerization reactor.